Reader device and method of signal amplification

ABSTRACT

Fluid collection devices, analysis instruments and methods for making and using same are disclosed. The fluid collection device is provided with a device and an electrochemical cell. The device has first and second walls defining a microfluidic channel, and a sample application port communicating with the microfluidic channel. The first wall and the second wall are spaced a distance less than 150 microns. The electrochemical cell is disposed on the first wall to contact a sample travelling through the microfluidic channel. The electrochemical cell comprising molecule receptors such that a physical property of the first electrochemical cell is effected upon one or more of the molecule receptors binding to an electroactive species within the sample.

CROSS-REFERENCE TO RELATED APPLICATIONS

The entirety of U.S. Provisional Application Ser. No. 61/665,353, filedon Jun. 28, 2012, is hereby expressly incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

Not Applicable.

BACKGROUND

A sensor (also called detector) is a device that measures a physicalquantity and converts it into a signal which may be read by an observeror by an instrument. For example, a mercury-in-glass thermometerconverts the measured temperature into expansion and contraction of aliquid which may be read on a calibrated glass tube. A thermocoupleconverts temperature to an output voltage which may be read by avoltmeter. For accuracy, most sensors are calibrated against knownstandards.

In biomedicine and biotechnology, sensors which detect analytes having abiological component, such as cells, protein, or nucleic acid are calledbiosensors. Biosensors may be used for both in vitro and in vivoapplications.

Typically, biosensors may be exposed to a biological specimen, such asblood or urine, and used to detect predetermined analytes within thebiological specimen. The biosensor may then be exposed to a transduceror detector element which may work in a physiochemical manner using asensing medium such as light, electricity, piezoelectric,electrochemical, or the like. In any event, the transducer or detectorelement transforms a signal from the biosensor into another signal thatmay be more easily measured and quantified. The signal produced by thetransducer or detector element may be provided to a reader device havingassociated electronics, signal processors, and/or a display to providethe results in a user readable format. For example, the results may beprovided on a graphical display.

In biomedicine and biotechnology, the amount of analytes of interestwithin a sample is very small and difficult to detect. As such,amplification of the signal may provide more accurate reading for adetected analyte. In particular, literature describes one method ofsignal amplification using oxidation and reduction of a species on aworking electrode provided with direct current (DC), which may beimbalanced by holding a working electrode at _200 mV and anotherelectrode at +50 mV. Alternating current (AC), however, is generally notused within the art, and if used, is solely for the determination ofadequacy of a sample volume, and the like. See, U.S. Patent PublicationNo. 2003/0098233, U.S. Patent Publication No. 2006/0175205, U.S. PatentPublication No. 2009/0020439, U.S. Patent Publication No. 2009/0181411,U.S. Patent Publication No. 2011/0284393, U.S. Pat. No. 6,843,263, andU.S. Pat. No. 7,473,397 which are all hereby incorporated by referencein their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate one or more implementationsdescribed herein and, together with the description, explain theseimplementations. In the drawings:

FIG. 1 is a block diagram of a sensor kit constructed in accordance withthe present disclosure.

FIG. 2 is an exploded view of an exemplary fluid collection deviceconstructed in accordance with the present disclosure.

FIG. 3 is a cross sectional view of a portion of a fluid collectiondevice constructed in accordance with the present disclosure.

FIG. 4 is a cross sectional view of a portion of another fluidcollection device constructed in accordance with the present disclosure.

FIG. 5 is a flow diagram illustrating an exemplary method fordetermining a concentration of a given constituent in a biologicalsample.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawings.The same reference numbers in different drawings may identify the sameor similar elements.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements, but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the inventive concept. Thisdescription should be read to include one or more and the singular alsoincludes the plural unless it is obvious that it is meant otherwise.

Further, use of the term “plurality” is meant to convey “more than one”unless expressly stated to the contrary.

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment.

Circuitry, as used herein, may be analog and/or digital, components, orone or more suitably programmed microprocessors and associated hardwareand software, or hardwired logic. Also, “components” may perform one ormore functions. The term “component,” may include hardware, such as aprocessor, an application specific integrated circuit (ASIC), or a fieldprogrammable gate array (FPGA), or a combination of hardware andsoftware. Software includes one or more computer executable instructionsthat when executed by one or more component cause the component toperform a specified function. It should be understood that thealgorithms described herein are stored on one or more non-transientmemory. Exemplary non-transient memory includes random access memory,read only memory, flash memory or the like. Such non-transient memorymay be electrically based or optically based.

Referring now to the Figures and in particular to FIG. 1, shown thereinis an exemplary sensor kit 10 constructed in accordance with the presentdisclosure. When the sensor kit 10 is used for analyzing biologicalsamples, the sensor kit 10 may be referred to as a biosensor kit. Ingeneral, the sensor kit 10 includes one or more fluid collection devices12, and an analysis instrument 14. Analysis instrument 14 may determinemeasurement and/or concentration of a given constituent in a sample 20provided to the one or more fluid collection devices 12. In oneembodiment, the fluid collection device 12 can be a test strip. Inparticular, the analysis instrument 14 may provide alternating current(AC) to the fluid collection device 12 to determine measurement and/orconcentration of a given constituent in the sample 20. The alternatingcurrent signal may have a voltage and frequency suitable to induce anelectric current across electrodes of the fluid collection device 12 toinduce redox cycling between the at least two electrodes in order tocreate an amplified signal which aids in the measurement and/orconcentration of the given constituent in the sample 20. During redoxcycling, one of the electrodes is a working electrode, and anotherelectrode is a counter electrode. When the alternating current signal isapplied to the working electrode and the counter electrode, the workingelectrode, for example, alternates between a collector mode and agenerator mode in rapid succession such that redox cycling occurs inorder to produce signal amplification.

As will be described in detail below, the sensor kit 10 can be usedwithin the healthcare industry for detecting measurements and/orconcentrations of the given constituent in the sample 20. In thisinstance, the sample 20 is a biological sample, such as blood, urine orsaliva collected from an animal, such as a human, or a non-human (suchas a cat, dog, cow, horse, fish, or the like). Alternatively, the sensorkit 10 can be used for detecting non-biological chemicals, such as lowlevel pesticide/agrochemicals in the environment or low levelcontaminants in water, for example.

The analysis instrument 14 may be provided with one or more signalgenerators 16 operable to provide an AC signal to the fluid collectiondevice 12, and one or more analytic measuring devices 18 operable toascertain presence and/or concentration of a given constituent of abiological sample 20 placed on the fluid collection device 12. Thesignal generator 16 and the analytic measuring device 18 may be asingular component or separate components. Generally, the analyticmeasuring device 18 may monitor current produced in response to ACcurrent applied by the signal generator 16 across the fluid collectiondevice 12.

In some embodiments, the signal generator 16 may be configured toprovide AC signal to one or more electrodes or electrochemical cells ofthe fluid collection device 12 as described in further detail herein.The AC signal may include a voltage suitable to induce an electriccurrent across at least two electrodes of the fluid collection device12. For example, in some embodiments, the AC signal may include avoltage of about 200 mV. Additionally, the AC signal provided may be ata low frequency. For example, the AC signal provided may be betweenapproximately 0.1 Hz-15 Hz and preferably between 0.5-2 Hz. Further, itshould be understood that it is intended that any and every numeralwithin any ranges specified herein, including the end points, is to beconsidered as having been stated. Thus, the range of approximately 0.1Hz-15 Hz is to be read as indicating each and every possible number inthe continuum between 0.1 Hz and 15 Hz.

The analytic measuring device 18 may be configured to ascertain at leastthe presence and/or concentration of a given constituent in the sample20. For example, the analytic measuring device 18 may be configured tomeasure electric current to ascertain the presence and/or concentrationof a given constituent in the sample 20. The analytic measuring device18 may also include circuitry and one or more other devices, such as aprinter or a display to provide results of the measurements in auser-perceivable format.

In some embodiments, the analytic measuring device 18 may include afluid collection device holder or slot for positioning at least onefluid collection device 12 therein. When the fluid collection device 12is located within the fluid collection device holder for positioning,the analytic measuring device 18 may be in electrical communication withthe fluid collection device 12. Holders are well known within the artand need no further description herein.

In some embodiments, the analysis instrument 14 may be provided with oneor more input devices 22. The one or more input devices 22 may permit auser and/or machine(s) to provide input into the signal generator 16and/or the analytic measuring device 18. Exemplary input devices 22 mayinclude, but are not limited to, one or more network port, one or morekeyboard (or keypad), one or more touchscreen, one or more mouse, and/orcombinations thereof. The analysis instrument 14 may also be providedwith one or more output devices 24. The one or more output devices 24may include, but are not limited to, displays, printers, network ports,and/or the like.

An exemplary fluid collection device 12 is illustrated in FIGS. 2 and 3.The fluid collection device 12 may be an electrochemical cell-basedbiosensor. The fluid collection device 12 may include a device 30, afirst electrochemical cell 32, and a second electrochemical cell 34. Inanother embodiment, as illustrated in FIG. 4, the fluid collectiondevice 12 may include the device 30 and a single electrochemical cell32.

Referring to FIGS. 2 and 3, the device 30 may include a first wall 40and an opposing second wall 42. The first wall 40 and the second wall 42may be opposing and may aid in defining a channel 44. The first wall 40may be spaced apart a distance d from the second wall 42. Optionally,one or more spacer layers 33 may be positioned between the first wall 40and the second wall 42. Generally, the one or more spacer layers 33 maybe thin layers (e.g., less than approximately 200 μm) and, in someembodiments, may also aid in defining the channel 44 as a microfluidicchannel. In some embodiments, the one or more spacer layers 33 may beformed of a pressure sensitive adhesive.

In some embodiments, the fluid collection device 12 may include a sampleinjection port 46 illustrated herein as an arrow. Any sample injectionport 46 known within the art or developed in the future may be used aslong as it provides at least a portion of the sample 20 to the channel44. Additionally, one or more additional channels or chambers may beincluded on or within the fluid collection device 12. For example, oneor more channels (e.g., wash chambers, waste port, and the like) knownin the art, or developed in the future, may be included on the fluidcollection device 12 as long as at least a portion of the biologicalsample 20 is provided to the channel 44 as described herein.

The device 30 may be constructed of material capable of exposure to thesample 20 including, but not limited to, epidermal cells, blood cells,plasma cells, urine, agricultural chemicals and/or the like, withoutsignificant deterioration or adverse results. For example, the device 30may be selected from a group including, but not limited to, paper,plastics, polymers, and combinations thereof.

The channel 44 may be defined by the first wall 40 and the opposingsecond wall 42. The channel 44 may aid in retention of at least aportion of the sample 20 positioned and/or injected via a sampleapplication port 46. The sample application port 46 may be in fluidiccommunication with the channel 44.

One or more enzymes 50 may be deposited on a surface of device 30 withinthe channel 44. In some embodiments, the one or more enzymes 50 may becoated on the first electrochemical cell 32 and/or the secondelectrochemical cell 34. Such enzymes 50 may be used within theoxidation/reduction cycle to aid in providing conversion of a givenconstituent in the biological sample 20 into a specific signal. Forexample, enzymes may encourage electrons from the given constituent inthe sample 20 to transfer to an oxidized form of a mediator molecule,thereby converting it to a reduced formation. Other bio-recognitionconstituents may also be deposited on the surface binding to the analyteof interest. For example, antiobodies, oligonucleotides and the likewould allow electrochemical labeling components to reside near or on thesurface to allow a specific signal. The mediator molecular may be asmall organic or inorganic chemical within the channel 44 that may becapable of existing in both an oxidized and a reduced formation.Mediator molecules generally tend to react quickly to donate or receiveelectrons. The mediator molecules may in turn provide electrons to thefirst electrochemical cell 32 and/or the second electrochemical cell 34of the fluid collection device 12. This series of reactions provideselectrochemical measurements capable of review using the analysisinstrument 14, illustrated in FIG. 1. Additionally reagents may beincluded in the fluid collection devices 12. For example, reagentsincluding, but not limited to, preservatives, surfactants, film formers,and the like, may be included in the channel 44 of the fluid collectiondevice 12.

Each electrochemical cell 32 and 34 may include two or more sensorcontacts and/or electrodes positioned adjacent to each one another. Forexample, in FIG. 2, the electrochemical cell 32 includes sensor contacts52, a first electrode 54, and a second electrode 56 positioned adjacentto the second electrode 54. In some embodiments, the electrodes 54 and56 may be confined to the area directly adjacent to the channel 44. Forexample, as illustrated in FIG. 2, the electrodes 54 and 56 do not spanthe length of the fluid collection device 12, but instead the electrodes54 and 56 are positioned directly adjacent to the channel 44. Forsimplicity, the electrochemical cells 32 and 34 will be discussed inreference to electrochemical cell 32 with the understanding that theconcepts described herein may apply to the electrodes of theelectrochemical cell 34 as further detailed herein.

The electrodes 54 and 56 may be formed of shapes including, but notlimited to, circular, square, triangular, rectangular, or any fancifulshape. For example, in FIG. 2, the electrodes 54 and 56 are formed incircular shapes. Although both electrodes 54 and 56 in FIG. 2 areillustrated with similar shapes, each electrode in the electrochemicalcell 32 and 34 may be formed in its own individual shape (e.g.,circular, fanciful). In some embodiments, the electrodes of eachelectrochemical cell 32 and 34 may be non-interdigitated. Althoughelectrodes 54 and 56 may generally be non-interdigitated, in someembodiments, electrodes 54 and 56 may be further shaped to increasesurface area adjacent to channel 44. Additional electrodes may also beincluded within each electrochemical cell 32.

In some embodiments, electrodes 54 and 56 may be planar electrodesformed of conductive material. The conductive material may include, butis not limited to, aluminum, gold, silver, copper, carbon nanotubes,graphene, platinum, and/or the like. In some embodiments, electrodes 54and 56 may be formed on device 30 using techniques including, but notlimited to, e-beam evaporation, filament evaporation, electroplating,sputtering, physical vapor deposition (PVD), chemical vapor deposition(CVD), PECVD (plasma-enhanced chemical vapor deposition), atomic layerdeposition (ALD), thin film deposition, nano-imprint lithography,jetting, and/or the like

Each electrochemical cell 32 and 34 may include one or more moleculereceptors for binding to one or more electroactive species within thesample 20 to affect a physical property of the electrochemical cells 32and 34 upon one or more electroactive species within the sample 20binding to the one or more molecule receptors.

The molecule receptors of the electrochemical cells 32 and 34 may bepositioned on the inside of the channel 44. At least a portion of themolecule receptors may be in fluidic contact with the channel 44. Ingeneral, the sample 20 having a given constituent (e.g., analyte) may bebrought into contact with a reagent having an enzyme 50 and a mediatorwithin the channel 44. As described herein, mediator molecules in thechannel 44 generally tend to react quickly to donate or receiveelectrons. The mediator molecules may in turn provide electrons to oneor more electrochemical cells 32 and/or 34.

As discussed above, the electrochemical cells 32 and 34 may include oneor more sensor contacts 52. The sensor contacts 52 may include one ormore conductors in electrical communication with electrodes 54 and 56 ofthe electrochemical cell 32. In some embodiments, the sensor contacts 52may provide electrical communication between the electrochemical cells32 and 34, and the analysis instrument 14 illustrated in FIG. 1.

The analytic measuring device 18 of the analysis instrument 14 mayreceive information detailing loss or gain of electrons providing aquantitative and/or qualitative measurement for analysis. For example,the electron oxidation/reduction cycle may affect the conductivity,resistance and/or capacitance measured across the electrodes 54 and 56.Even further, in embodiments wherein two electrochemical cells 32 and 34are present, electron binding may affect the conductivity, resistanceand/or capacitance measured across the electrochemical cells 32 and 34.

Referring to FIGS. 2 and 4, in some embodiments, the fluid collectiondevice 12 may include a single electrochemical cell 32. The singleelectrochemical cell 32 may include electrodes providing measurementsindicative of the presence and/or concentration of a given constituentof the sample and/or fill detection. Fill detection is generally amanner of determining whether the microfluidic chamber 44 includes aconcentration of the sample 20 suitable for providing an accurate and/orprecise measurement. Alternatively, visual confirmation of the fill, oradditional electrodes (besides those mentioned herein) may be used forfill confirmation.

The design of the single electrochemical cell 32 may include atwo-electrode design wherein the first electrode 54 is a counterelectrode, and the second electrode 56 is a working electrode asillustrated in FIG. 2. Alternatively, the design of the single electrode32 may include a four electrode design (e.g. multiple working electrodes(comprising two electrodes), a counter electrode and a referenceelectrode). In another embodiment, the design of the singleelectrochemical cell 32 may be constructed as a three electrode designhaving a counter electrode, a working electrode and a referenceelectrode. Multiple electrodes may further be added based on designconsiderations.

The fluid collection device 12 may include a dual electrochemical celldesign having a first electrochemical cell 32 and a secondelectrochemical cell 34 as illustrated in FIG. 3. Generally, the firstelectrochemical cell 32 may be positioned on the first wall 40 and thesecond electrochemical cell 34 may be positioned on the second wall 42.The first wall 40 and the second wall 42 may be separated by a distanced. The distance d may influence the signal amplification for detectionof presence and/or concentration of a given constituent in thebiological sample 20. To increase signal amplification, the distance dmay be less than 200 μm. In some embodiments, the distanced may bebetween 80-100 μm.

In the design of the single electrochemical cell 32 as illustrated inFIG. 4, the electrochemical cell 132 may be solely positioned on thefirst wall 40 or the second wall 42. For example, in FIG. 4, the singleelectrochemical cell 132 is positioned on second wall 42. The first wall40 and the second wall 42 may be separated by a distance d. Confinementof the electrochemical cell 132 within a small space may increase signalamplification for detection of presence and/or concentration of a givenconstituent in the sample 20. In some embodiments, the first wall 40 andthe second wall 42 may be positioned such that the distance d is lessthan approximately 200 μm. For example, the first wall 40 and the secondwall 42 may be positioned such that the distance d is between 50-200 μm.

FIG. 5 illustrates an exemplary method 100 for obtaining the presenceand concentration of a given constituent of the sample 20 using thesensor kit 10. In a step 102, the sample 20 may be positioned in thesample injection port 46 of the fluid collection device 12. In someembodiments, the sample 20 may travel the through one or more channelsor chambers on the fluid collection device 12 prior to arriving in thechannel 44. In a step 104, a fill detection method may be used todetermine if the concentration of the sample 20 is adequate within thechannel 44 for an accurate and/or precise result.

In a step 106, an EDL charging current may be supplied from the signalgenerator 16 to the first electrochemical cell 32 and/or the secondelectrochemical cell 34. EDL stands for “Electric Double Layer”, whichis a region (˜0.1-10 nm) at an interface between the electrodes 54 and56 and an electrolyte within the sample 20 where the electrolyte takeson a local charge. Alternating current sensor analysis may neglect anycurrent that would be measured from the changing electric field (e.g.,EDL charging current). In other words, when the potential in theelectrodes 54 and/or 56 changes, an electric field across theelectrode/electrolyte interface (EDL) also changes forming a timevarying electric field having an associated current (called‘displacement current’ or ‘charging current’) that is measurable by theanalytical measuring device 18 even without the presence of theelectrochemical reaction. Neglecting the EDL charging current can enablerecognition of an analyte with less signal background interference andwith reduced measurement time due to the time dependence usuallyassociated with the EDL charging current. Analysis of the subsequentelectron transfer kinetics may also be enhanced due to the lack ofinterference of the EDL charging current allowing more specific analysisand signal reports of such analytes.

In some embodiments, multiple signal generators 16 may be used. Forexample, a first signal generator 16 may provide AC to the firstelectrochemical cell 32 and a second signal generator 16 may provide ACto the second electrochemical cell 34. In this regard, the signalgenerator 16 may provide signals out of phase (i.e., asynchronous)between the two electrochemical cells 32 and 34 or in the same phase(i.e., synchronous).

Once AC is applied to the first electrochemical cell 32 and/or thesecond electrochemical cell 34, the oxidation/reduction cycle of thegiven constituent of the sample 20 may occur providing a measureablereading for the analytic measuring device 18. In a step 110, theanalytic measuring device 18 may perform an analysis to provide theconcentration of the given constituent of the sample 20. In someembodiments, amperometric analysis may be performed. In otherembodiments, coulometric or voltammetry analysis may be performed. Forexample, signal averaging and peak sensing can be applied to a resultingsinusoidal AC response. Further treatment of the signal would allowconcentration analysis to the analyte of interest.

The signal generator 16 may also be configured to provide (1) a “rest”step of a predetermined time period, and/or (2) an imbalanced polarity,such as −200 mV switching to +150 mV. The predetermined time period ofthe rest step may be from 1 to 500 milliseconds, for example beforeswitching the polarity.

In some embodiments, multiple fluid collection devices 12 and readingsmay be performed to provide calibration of the analysis instrument 14.

To use the analysis instrument 14, the fluid collection device 12 havinga biological sample, for example, is introduced to the analysisinstrument 14. The fluid collection device 12 can be introduced to theanalysis instrument 14 by a user connecting the sensor contacts 52 tocontacts or electrodes of the analysis instrument 14. For example, theanalysis instrument 14 may have a port (not shown) adapted to receiveone or more of the fluid collection devices 12 whereupon insertion ofthe one or more fluid collection devices 12 into the port, the sensorcontacts 52 are automatically connected to the sensor contacts of theanalysis instrument 14. As discussed above, the analysis instrument 14is configured to (1) provide the alternating current signal to at leasttwo electrodes of at least one of the first and second electrochemicalcells 32 and 34 of the biosensor interacting with the biological sampleof the fluid collection device 12. Further, as discussed above, thealternating current signal has a voltage suitable to induce an electriccurrent across the two electrodes, and (2) measure electric current toascertain at least one of a concentration and presence of a givenconstituent of the biological sample.

As another example, the fluid collection device 12 can be read asfollows. An alternating current signal can be applied across at leasttwo electrodes of at least one of the first and second electrochemicalcells 32 and 34 having the sample 20 applied thereto. The alternatingcurrent signal has a voltage and frequency suitable to induce anelectric current across the two electrodes to induce redox cyclingbetween the at least two electrodes to create an amplified signal. Thecurrent of the amplified signal is measured and correlated withpredetermined information to ascertain at least one of a concentrationand presence of a given electroactive species of the sample.

The foregoing description provides illustration and description, but isnot intended to be exhaustive or to limit the inventive concepts to theprecise form disclosed. Modifications and variations are possible inlight of the above teachings or may be acquired from practice of themethodologies set forth in the present disclosure.

Also, certain portions of the implementations may have been described as“components” or circuitry that performs one or more functions. The term“component” or “circuitry” may include hardware, such as a processor, anapplication specific integrated circuit (ASIC), or a field programmablegate array (FPGA), or a combination of hardware and software.

Even though particular combinations of features are recited in theclaims and/or disclosed in the specification, these combinations are notintended to limit the disclosure. In fact, many of these features may becombined in ways not specifically recited in the claims and/or disclosedin the specification. Although each dependent claim listed below maydirectly depend on only one other claim, the disclosure includes eachdependent claim in combination with every other claim in the claim set.

No element, act, or instruction used in the present application shouldbe construed as critical or essential to the invention unless explicitlydescribed as such outside of the preferred embodiment. Further, thephrase “based on” is intended to mean “based, at least in part, on”unless explicitly stated otherwise.

1-25. (canceled)
 26. An analysis instrument, comprising: a signalgenerator configured to provide an alternating current signal to atleast two electrodes of an electrochemical cell of a sensor, thealternating current signal having a voltage and frequency suitable forinducing redox cycling between the at least two electrodes to create anamplified signal across the two electrodes; and an analytical measuringdevice to ascertain at least one concentration of a given constituent ofa sample by measuring the amplified signal.
 27. The analysis instrumentof claim 26, wherein the frequency is in a range from approximately 0.1Hz to 15 Hz.
 28. The analysis instrument of claim 27, wherein theelectrochemical cell is a first electrochemical cell, the alternatingcurrent signal is a first alternating current signal, the voltage is afirst voltage, and the amplified signal is a first amplified signal; andwherein the signal generator is configured to provide a secondalternating current signal to at least two electrodes of a secondelectrochemical cell of the sensor, the second alternating currentsignal having a second voltage and a second frequency suitable to induceredox cycling across the two electrodes to generate a second amplifiedsignal; and wherein the analytical measuring device is configured toascertain at least one of a presence and a quantity of a givenconstituent of a sample by measuring the first and second amplifiedsignals.